Morphological changes in mitochondria during mechanical unloading observed on electron microscopy: a case report of a bridge to complete recovery in a patient with idiopathic dilated cardiomyopathy.

The recovery of the cardiac function under mechanical support has not been well documented from a histopathological point of view. We herein report a case of idiopathic dilated cardiomyopathy in which the patient showed a complete recovery of the systolic function following treatment with a left ventricular assist device (LVAD) for deteriorated heart failure. A light microscopic observation showed marked regression of hypertrophic myocytes with significant intracellular vacuolization and scarcity at the time of LVAD implantation after the administration of mechanical support. Furthermore, an electron microscopic observation revealed that these findings were regulated primarily by volumetric regression and morphometric improvements in cardiomyocytic mitochondria.